Aquametry or the determination of water in a material is an important branch of chemical analysis. The most common chemical analysis method for the determination of water is the Karl Fischer titration. However, other chemical analysis methods, such as Gas Chromatography (GC), are also widely used; see Gilbert et al., Anal. Chem., 2001, p520-526.
When most chemical analysis instruments are used to determine water in a liquid, the instrument must be calibrated by analyzing a liquid “standard” having a known water concentration. Calibrating a chemical analysis instrument for the determination of water at relatively low concentrations (e.g., in the range of 1 part per million) is difficult because it is difficult to prepare a liquid standard having such a relatively low water concentration because water from the environment tends to contaminate the liquid standard.
Normal phase liquid chromatography (NPLC)is an important chemical analysis technique, see Heftmann, Journal of Chromatography Library, Volume 22A, pages A75-A78. However, the water concentration of the relatively non-polar mobile phase used in NPLC has a significant effect on the relative elution rate of the separated components of interest. Therefore, the mobile phase used in NPLC is usually kept as free of water as possible and/or a relatively polar “modulator”, such as an alcohol is added to the mobile phase.